Field of the Invention
The present invention relates to a drying device for drying elongated work pieces, in particular work pieces being coated with paint, lacquer or the like, in a continuous process.
Description of Related Art
Elongated work pieces, in particular of wood or plastics, are coated at least in part, for example after profiling. Here, coating is performed in a continuous process in which the work piece is moved through a chamber, for example, in which for example all surfaces, only individual edges etc. are coated in particular with paint, lacquer or the like. Such a device for coating elongated work pieces in a continuous process is described for example in European Application Nos. EP 10 162 699 and EP 11 174 355.
Drying has to be performed immediately after coating, in particular after coating an edge of an elongated workpiece. For this purpose it is known to provide a drying device directly after the coating device. The work piece is also transported through the drying device in a continuous process. It is known to carry out the drying by means of heat sources such as infrared lamps. This is described for example in European Patent No. EP 1 144 129.
It is a problem of such drying devices that for example a layer of paint or lacquer does not dry thoroughly, but that a dry, dense skin, a so-called film, is formed at the surface and wet paint or lacquer remains thereunder. This may for example lead to blistering during the further drying process. If the product is packaged in film materials, for example, the residual water from the lacquer is later visible as water drops in the packaged product. Further, it is demanded that the passage times are short in order to keep the production costs, in particular the power consumption, low. The formation of a film is particularly critical with film-forming lacquers, in particular with such lacquers having a high proportion of solid particles.
Specifically, it is demanded that the drying should remove more than 90%, preferably more than 92% of the water in the coating material. Packing the elongated work pieces, in particular glass/rock wool boards, is possible only with the proportion of water appropriately reduced, since otherwise condensate may be formed.